isMixedCase function
Returns true if the token is mixed-case (e.g., 'OpenAI').
Implementation
bool isMixedCase(String token) {
if (token.length < minMixedCaseTokenLength) return false;
final String alpha = token.replaceAll(RegExp(r'[^A-Za-z]'), '');
if (alpha.isEmpty) return false;
bool hasUpper = false;
bool hasLower = false;
// Check if we have both upper and lower after the first character
// (Title Case is handled separately by the dictionary)
for (int i = 1; i < alpha.length; i++) {
if (alpha[i] == alpha[i].toUpperCase()) hasUpper = true;
if (alpha[i] == alpha[i].toLowerCase()) hasLower = true;
}
return hasUpper && hasLower;
}